The invention relates to an anti-theft device for an audio set which is slidingly installed in an installation recess of a motor vehicle, and which has an actuatable theft module controlled by a change-over switch which s actuated to prevent operation of the audio set when the audio set is pulled out of the installation recess. A change-over switch is provided which has at least one switching position wherein it is electrically connected through a first plug connection, at the rear wall of the audio set and with a theft module in the audio set. The switch means is movable to a second position upon an unauthorized pulling out of the audio set to cause actuation of the theft module as a result of a change of electrical potential, created by the switch. The audio set additionally has a second plug connection with a power supply from the wiring system of the motor vehicle to run the audio set.
An anti-theft device of this general type is known from German Patent Application No. (DE-PS) 36 19 523, which corresponds to U.S. patent application Ser. No. 060,315, filed June 10, 1987 now U.S. Pat. No. 4,805,233. There, the change-over switch is integrated into an audio housing and changes a theft module input from the ground potential to a positive potential, and thus renders the audio set inoperative in the case of an unauthorized removal of the audio set.
Although such an integrated change-over switch has the advantage that it is securely actuated during the installation and the removal of the audio set and thus responds reliably, it has the disadvantage that an installation space must also be provided for the change-over switch as well as an opening for the mechanism actuating it (switching spring, switching lever, switching tappet) in the audio set housing itself.
One object of the invention is to provide a similar type of an anti-theft device such that, while the security with respect to error functions is maintained, no installation of a switch mechanism has to be carried at the audio set itself.
The objects of the invention are obtained by providing a separate housing means for containing the change-over switch, as well as first and second output plug connection elements which mate with plug connection elements at the rear wall of the audio set. These connections elements provide for a change-over in potential to the theft module from the wiring system of the motor vehicle when the change-over switch is actuated.
Also provided are connection elements with the wiring system of the vehicle into the housing itself. The housing has two multiple pole input plug connecting elements and a line connection for the audio set is led from a pole of one of the plug connection elements to a pole of the second input plug connection element, and from another pole of the second input plug connection element to a pole of one of the output plug connection elements.
This line connection is closed by a bridge between two poles of a cable plug which is inserted into the second input plug connection element for operation of the anti-theft device, but is not required for directing the power supply to the audio set itself.
In such an operation, it is desirable that the change-over switch be a microswitch operated by a switching lever which is triggered upon removal of the audio set from the recess. Upon removal of the audio set, the microswitch is then activated to change a ground connection to the anti-theft device to a positive source of power from the wiring system of the vehicle.
In addition, a burglar alarm system means is connected to the audio set by the second input plug connection element and the change-over switch in the housing. Thus, when a change of potential occurs at either the change-over switch or the theft module, the burglar alarm will be triggered due to the change of potential.
Additionally, one can provide a key operated switch which directly controls the theft module in order to render the audio set inoperative.
Additionally, mechanically pull off protectors which are well known to those skilled in the art are provided at all plug elements and cable plug means.
Although the electric change-over switch controlling the theft module must no longer be arranged directly in the housing of the audio set, it is, by the integration into a joint housing with plug connection elements which, among other things, are used for supplying current to the audio set, inevitable coupled with it. Thus, after the proper connecting of the plug connections, the change-over switch is inevitably in the position that is appropriate for its objective.
Plug-type connections with assigned electrical switches are known per se (Catalogue DS 4/410, Edition 1, "Steckverbinder" (Pin and Socket Connectors) of Hirschmann Co., Esslingen, Page 178/179); and from DE-AS No. 29 08 157, a multiple-pole trailer socket is known with a switch-off device for the rear fog light of the towing vehicle.
In the case of these plug connections, the respective change-over or break switch is arranged at the socket and is, in each case, actuated by the corresponding plug.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.